Linear bearings have long existed for supporting a tube or rod, most commonly a tube or rod having a tubular outer periphery, to slide linearly within or along the bearing. One common prior art bearing has a sets of roller bearings mounted between angled linearly extending braces. The roller bearings have rounded circumferential edges adapted to abut the external periphery of the tube or rod slidably mounted within the linear bearing, and in the case of a square tube or rod (i.e., having a square cross-section), the sets roller bearings similarly abut the planar sides of the square rod so that the square rod may slide within the linear bearing.
This linear roller bearing type of prior art often does not sufficiently secure the polygonal tube or rod from responding to external forces on the rod by rotating at least somewhat about the axis of the rod. Similarly, these type of prior art bearings also often do not sufficiently prevent the tube or rod from responding to external force by moving laterally (to the side with respect to the rod axis) intermediate the locations of the roller bearings spaced about the axis of the linear roller bearing. These issues are particularly problematic in heavy duty environments.
Another type of linear bearing utilizes V-groove bearings mounted to a single laterally extending triangular plate (i.e., extending parallel to a central linear axis of the bearing) or a single relatively narrow bracket transverse to the axis of the rod that may slide with respect to the linear V-groove bearing. These types of V-groove linear bearings are typically used to slide along a fixed rectangular or other tube or rod with the V-groove edge of the bearings slidable along two to four external corners on the tube rod extending parallel to the axis of the rod.
These types of V-groove linear bearings do not provide sufficient structural strength to prevent a non-fixed tube or rod, particularly a heavy-duty tube rod, from rotating around the linear bearing axis, or from moving side to side with respect to the linear bearing or its axis. Thus, they have typically not been used to support a tube or rod that slides with respect to the linear bearing and the linear bearing is the structure that maintains the sliding rod in position rotationally and side-to-side with respect to the linear bearing or its axis.
Yet another type of prior art linear bearing, shown in U.S. Pat. No. 2,907,761, provides an outer fixed tube housing with two opposed bearing mounting brackets mounted to, and extending laterally along, the interior of the fixed tube housing. The opposed bearing mounting brackets cooperatively provide four parallel U-shaped channels extending laterally along the brackets within the fixed tube housing, and multiple sets of two opposed V-groove bearing assemblies mounted along the laterally extending the U-shaped channels. Four corners extending outwardly from a linearly sliding rod penetrate the V-groove slots in the bearings. Although this V-groove linear bearing secures the rod in slidably in position rotationally and side-to-side with respect to this linear bearing, this bearing has a complex structure that is difficult and relatively expensive to manufacture and is bulky, heavy, and costly to ship.